Tuesday, December 18, 2012

Life Expectancy

4:27 PM

Life expectancy is the expected (in the statistical sense) number of years of life remaining at a given age.
Life expectancy at birth during the time of the Roman Empire was about 28 years. At the beginning of the 20th century, global average life expectancy was just 31 years, and below 50 years in even the richest countries. Today, life expectancy in Canada and its peer countries is 81 years. This varies widely by region: humans live on average 32 years in Swaziland and 83 years in Japan.

Longevity is positively related to education and income. Longevity is increasing with medical advances and adoption of healthier lifestyles. In fact, life expectancy has increased by a full 10 years in the last 50 years.

The life expectancy at birth in Canada was 81.1 years in 2009. Life expectancy has increased by 6.2 years since 1979, when it was 74.9 years. The increase in life expectancy is expected to continue indefinitely.

Gender differences

Women tend to have a lower mortality rate at every age. Life expectancy at birth in Canada in 2009 was 78.8 years for men and 83.3 years for women. The gap between men and women has narrowed over time from 7.4 years in 1979 to just 4.5 years in 2009.

Average life expectancy at age 65 is in the mid- to late 80s. For a 65 year old couple, there is a 50% chance that one will be living to age 91 and a 25% chance that one will be living to age 95.

Regional differences

Canadians can expect to live three years longer than Americans. This gap has been increasing and this trend is expected to continue in the future.

Life expectancy also varies by region in Canada. While the average life expectancy at birth for the country as a whole was 81.1 in 2009, it ranged from a low of 75.1 years in the territories (Yukon, Northwest Territories and Nunavut) to a high of 81.7 in British Columbia. Three provinces beat the average: British Columbia, Ontario and Quebec.

Healthy life expectancy

The Healthy Life Years indicator (HLY) is a European indicator that measures population health. It combines mortality and morbidity data to represent overall population health in a single indicator. HLY measures the number of remaining years that a person of a certain age is expected to live without disability. In other words, it measures the disability-free life expectancy.

The chart below compares the proportion of a person's life spent in good health for various industrialized countries.

Health-adjusted life expectancy (HALE)

A similar concept related to HLY is the health-adjusted life expectancy (HALE). Life expectancy is sometimes criticized as putting too much emphasis on quantity of life, as opposed to quality of life.
HALE weighs years of life according to health status by subtracting from life expectancy average years of ill-health weighted for severity of health problems.

For example, in 2007 Canada's general life expectancy was 80.7 years, but of those years 73 could be expected to be healthy. So the average Canadian could expect to live about 90% of his or her life in good health.

Interestingly, although women have higher life expectancy than men, men have a higher HALE than women. For 2007, men were expected to spend 88% of their life in good health, compared to 85.8% for women.

The key point is that even if demographers expect HALE to increase in the future, our final years will be spent with declining health and the associated personal and societal costs of care.

Maximum lifespan

Maximum lifespan refers to the maximum amount of time a member of a species can survive between birth and death. In other words, it is the upper boundary of life.

The oldest confirmed recorded age for any human is 122 years, a feat achieved by Jeanne Calment, a French widow who passed away in 1997. The maximum lifespan of a chimpanzee is 59 years. For a horse, it is 62 years. Here are a few species that have much longer maximum lifespans than us:

Galapagos tortoise

150 years

Lobster

170 years

Koi fish

200 years

Red sea urchin

200+ years

Bowhead whale

211 years

Bristlecone pine

1,000s of years

Jellyfish (Turritopsis nutricula)

Immortal

Hydra

Immortal

Immortality is possible! The cells of hydras continually divide and this allows defects and toxins to be diluted. They do not undergo “senescence”, and, as such, are biologically immortal. Turritopsis nutricula is a small (5 millimeters) species of jellyfish that converts its cells (transdifferentiation). This process can repeat indefinitely, also rendering it biologically immortal.

Leading causes of death

Alas, we do not possess the genetic qualities for living such a long time. How can we make the most of what we have? The answer seems to lie in what we eat and the amount of physical activity we do.

According to the U.S. National Vital Statistics Reports (Vol. 60, No. 4), the leading causes of death in 2010 were diseases of the heart and malignant neoplasm, each accounting to about 25% of deaths. Chronic lower respiratory diseases, cerebrovascular diseases and accidents accounted for about 5% each of the deaths. The rest was attributed to other causes, each amounting to a 2.5% or less.

"Uprooting the Leading Causes of Death" is an excellent – and entertaining – video by Dr. Michael Greger that offers practical advice on how best to feed ourselves to prevent, treat, and even reverse many of the top 15 causes of death.